OVDs are used as security elements for example for banknotes, security documents or labels for goods. As their optical effect is based for example on light refraction or light diffraction at optical microstructures they cannot be counterfeited with colour copying processes.
Optically variable security elements have been proposed, which afford different optical effects in a plurality of layers:
WO 01/03945 A1 describes a security element having a transparent substrate, on one side of which there is applied a thin film which produces a perceptible colour shift in dependence on the viewing angle of the person viewing it. A diffraction pattern is applied on the opposite side of the transparent substrate to further enhance the copy protection. That diffraction pattern acts as a diffraction grating so that for example the illusion of a three-dimensional image can be created for the person viewing it by means of that two-dimensional pattern. That provides that the optical effects produced by the thin film layer and the optical effects produced by the diffractive pattern are superposed at any location of the optically variable security element and thus that affords overall an optical effect which is composed of those two effects.
WO 02/00445 A1 proposes measures for decoupling the optical effects produced in a plurality of layers of an optically variable security element, from each other. For that purpose, one possibility proposed is that of applying an opaque layer between a relief structure which produces a holographic image by means of diffraction and a thin film which produces a colour change. A further option proposed is that of arranging, in place of the opaque intermediate layer, one or more highly refractive layers and an adhesive layer. Those layers increase reflection and thus the strength of light in the region of the relief structure producing the holographic image and the holographic image is thus evident in relation to the colour shift effect of the thin film.
It is further known to use elements for radio frequency identification (RFID) as anti-theft means and for goods identification. RFID is based on wireless radio frequency communication between a transponder which is allocated to an object or a person, and a reading device. The transponder usually includes an antenna connected to a semiconductor chip. The communication between the transponder and the reading device usually involves a communication of an identification code from the transponder to the reading device.
For example U.S. Pat. No. 4,220,956 describes a manufacturing method for an RF antenna for an RFID transponder, in which the antenna is produced by etching a conductive layer of a thickness of <125 μm which is applied on one side of a thin substrate. In that case the etching process is like that for the production of printed circuits in the electronic industry.